The sun is luminous because it produces its own light through nuclear fusion. Earth and the moon are non-luminous, meaning they do not produce their own light.

Here's why:

* Earth and the moon reflect light. They shine because they reflect sunlight. Think of them like mirrors, reflecting the sun's light towards us.

* Earth's atmosphere scatters sunlight. This is why we see a blue sky during the day.

So, while Earth and the moon appear bright, they are only reflecting the sun's light.